Traffic Characteristic Based Selection of Serving Base Station

1. A method of selecting a base station to be used as a serving base station of a mobile terminal, the method comprising: determining a traffic characteristic of the mobile terminal; wherein determining the traffic characteristic comprises: determining a first fill level of a buffer for storing downlink data to be transmitted to the mobile terminal; determining a second fill level of a buffer for storing uplink data to be transmitted from the mobile terminal; determining the traffic characteristic from the first fill level and the second fill level; selecting, based on the traffic characteristic, between: a first mode in which the base station to be used as the serving base station is selected based on the selected base station's downlink radio capacity as compared to one or more other base stations; a second mode in which the base station to be used as the serving base station is selected based on the selected base station's uplink radio capacity as compared to one or more other base stations.

2. The method of claim 1 , wherein the traffic characteristic of the mobile terminal indicates an asymmetry between uplink data traffic of the mobile terminal and downlink data traffic of the mobile terminal.

3. The method of claim 2 , further comprising selecting the first mode in response to the traffic characteristic of the mobile terminal indicating a downlink oriented asymmetry.

4. The method of claim 2 , further comprising selecting the second mode in response to the traffic characteristic of the mobile terminal indicating an uplink oriented asymmetry.

5. The method of claim 2 , further comprising: determining an amount of downlink data transmitted to the mobile terminal during a period of time; determining an amount of uplink data transmitted from the mobile terminal during the period of time; wherein the determining the traffic characteristic further comprises determining the traffic characteristic also from the amount of downlink data and the amount of uplink data.

6. The method of claim 5 , wherein the period of time is longer than 20 milliseconds.

7. The method of claim 1 , further comprising: averaging the first fill level; averaging the second fill level; determining the traffic characteristic from the averaged first fill level and the averaged second fill level.

8. The method of claim 1 , further comprising: normalizing the first fill level with a downlink data rate that can be achieved for transmission of the downlink data to the mobile terminal; normalizing the second fill level with an uplink data rate that can be achieved for transmission of the uplink data from the mobile terminal; determining the traffic characteristic from the normalized first fill level and the normalized second fill level.

9. The method of claim 8 , further comprising: further normalizing the first fill level with a downlink resource utilization value of the mobile terminal; further normalizing the second fill level with an uplink resource utilization value of the mobile terminal.

10. The method of claim 1 , further comprising: receiving a buffer status report from the mobile terminal; determining the second fill level from the buffer status report.

11. The method of claim 2 , further comprising: detecting a quality of service class of a service used at the mobile terminal; determining the asymmetry between uplink data traffic of the mobile terminal and downlink data traffic of the mobile terminal from the quality of service class.

12. The method of claim 1 , wherein the downlink radio capacity is based on a received signal power of a signal transmitted from the base station to the mobile terminal.

13. The method of claim 1 , wherein the downlink radio capacity is based on an amount of downlink radio resources which are available at the base station.

14. The method of claim 1 , wherein the uplink capacity is based on a pathloss of a signal transmitted from the mobile terminal to the base station.

15. The method of claim 1 , wherein the uplink radio capacity is based on an amount of uplink radio resources which are available at the base station.

16. The method of claim 1 , further comprising initiating handover of the mobile terminal to the base station selected to be used as the serving base station.

17. A base station, comprising: a radio interface to send downlink transmissions to a mobile terminal and to receive uplink transmissions from the mobile terminal; a processor configured to select a base station to be used as a serving base station of the mobile terminal, wherein the processor is configured to: determine a traffic characteristic of the mobile terminal; wherein determining the traffic characteristic comprises: determining a first fill level of a buffer for storing downlink data to be transmitted to the mobile terminal; determining a second fill level of a buffer for storing uplink data to be transmitted from the mobile terminal; determining the traffic characteristic from the first fill level and the second fill level; select, based on the traffic characteristic, between: a first mode in which the processor is configured to select the base station to be used as the serving base station based on the selected base station's downlink radio capacity as compared to one or more other base stations; a second mode in which the processor is configured to select the base station to be used as the serving base station based the selected base station's uplink radio capacity as compared to one or more other base stations.

18. The base station of claim 17 , wherein the traffic characteristic of the mobile terminal indicates an asymmetry between uplink data traffic of the mobile terminal and downlink data traffic of the mobile terminal.

19. A computer program product stored in a non-transitory computer readable medium for controlling a base station, the computer program product comprising software instructions which, when run on a processor of the base station, causes the processor to: determine a traffic characteristic of the mobile terminal; wherein determining the traffic characteristic comprises: determining a first fill level of a buffer for storing downlink data to be transmitted to the mobile terminal; determining a second fill level of a buffer for storing uplink data to be transmitted from the mobile terminal; determining the traffic characteristic from the first fill level and the second fill level; select, based on the traffic characteristic, between: a first mode in which the base station to be used as the serving base station is selected based on the selected base station's downlink radio capacity as compared to one or more other base stations; a second mode in which the base station to be used as the serving base station is selected based on the selected base station's uplink radio capacity as compared to one or more other base stations.